第15章：Scalaの制御構造 ref: http://qiita.com/f81@github/items/b64832468d112b4c9597

file10.scala

scala> {
     |   val variable = "a"
     |   val variable = "b"
     | }
<console>:10: error: variable is already defined as value variable
                    val variable = "b"
                        ^

file11.scala

scala> {
     |   val variable = "a"
     |
     |   {
     |     println(variable)
     |   }
     | }
a

file12.scala

scala> {
     |   val variable = "a"
     |
     |   {
     |     val variable = "b"
     |     println(variable)
     |   }
     | }
b

file13.scala

throw new FileNotFoundException

file14.scala

scala> throw new java.io.FileNotFoundException
java.io.FileNotFoundException
        at .<init>(<console>:8)
        at .<clinit>(<console>)
        at .<init>(<console>:11)
        at .<clinit>(<console>)
        at $print(<console>)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:601)
        at scala.tools.nsc.interpreter.IMain$ReadEvalPrint.call(IMain.scala:704)
        at scala.tools.nsc.interpreter.IMain$Request$$anonfun$14.apply(IMain.scala:920)
        at scala.tools.nsc.interpreter.Line$$anonfun$1.apply$mcV$sp(Line.scala:43)
        at scala.tools.nsc.io.package$$anon$2.run(package.scala:25)
        at java.lang.Thread.run(Thread.java:722)

file15.scala

scala> try {
     |   val input = new java.io.FileInputStream("input.txt")
     | } catch {
     |   case ex: java.io.FileNotFoundException => println("File not found")
     |   case ex: java.io.IOException => println("IOError")
     | }
File not found

file16.scala

scala> {
     |   val input = new java.io.FileInputStream("input.txt")
     |
     |   try {
     |     throw new java.io.IOException // 明示的に例外をスロー
     |
     |     input.close() // 例外がスローされているので、ここには到達しない
     |   } catch {
     |     case ex: java.io.FileNotFoundException => println("File not found")
     |     case ex: java.io.IOException => println("IOError")
     |   } finally {
     |     println("Finally")
     |     input.close()  // 例外が発生しても、しなくてもここに入ってくる
     |   }
     | }
IOError
Finally

file2.scala

scala> val list = List("Brad Jones", "Steven Gerrard", "Daniel Agger", "Daniel Sturridge")
list: List[java.lang.String] = List(Brad Jones, Steven Gerrard, Daniel Agger, Daniel Sturridge)

scala> for (name <- list) { println(name) }
Brad Jones
Steven Gerrard
Daniel Agger
Daniel Sturridge

file3.scala

scala> for (name <- list if name.startsWith("Daniel")) { println(name) }
Daniel Agger
Daniel Sturridge

file5.scala

for (name <- list if name.startsWith("Daniel")) { println(name) }

file6.java

final Iterator<String> iterator = new FilterIterator(list.iterator(),
        new Predicate() {

            @Override
            public boolean evaluate(Object object) {
                final String name = (String) object;
                return StringUtils.startsWith(name, "Daniel");
            }
        });

while (iterator.hasNext()) {
    System.out.println(iterator.next());
}

file7.scala

scala> val daniels = for { name <- list if name.startsWith("Daniel") } yield name
daniels: List[java.lang.String] = List(Daniel Agger, Daniel Sturridge)

scala> for (name <- daniels) { println(name) }
Daniel Agger
Daniel Sturridge

file8.scala

scala> var count = 0;
count: Int = 0

scala> while (count < 5) {
     |   count += 1
     |   println(count)
     | }
1
2
3
4
5

file9.scala

scala> var count = 0;
count: Int = 0

scala> do {
     |   count += 1
     |   println(count)
     | } while (count < 5)
1
2
3
4
5

IfTest1.scala

import java.io.File

object IfTest1 {

  def main(args: Array[String]): Unit = {
    var filename = "config.txt"

    if (!args.isEmpty)
      filename = args(0)

    println("Filename:" + filename)
  }

}

IfTest1Refactor.scala

import java.io.File

object IfTest1Refactor {

  def main(args: Array[String]): Unit = {
    val filename = if (args.isEmpty) "config.txt" else args(0)

    println("Filename:" + filename)
  }

}

JavaFiltering.java

import java.util.Arrays;
import java.util.Iterator;
import java.util.List;

import org.apache.commons.collections.Predicate;
import org.apache.commons.collections.iterators.FilterIterator;
import org.apache.commons.lang3.StringUtils;

public class JavaFiltering {

    public static void main(String[] args) {
        final List<String> list = Arrays.asList("Brad Jones", "Steven Gerrard",
                "Daniel Agger", "Daniel Sturridge");

        final Iterator<String> iterator = new FilterIterator(list.iterator(),
                new Predicate() {

                    @Override
                    public boolean evaluate(Object object) {
                        final String name = (String) object;
                        return StringUtils.startsWith(name, "Daniel");
                    }
                });

        while (iterator.hasNext()) {
            System.out.println(iterator.next());
        }
    }

}